X-ray devices such as handheld x-ray fluorescence (XRF) instruments are known as are various shields for such instruments. See U.S. Pat. Nos. 7,430,274; 7,375,359; 7,375,358; 6,965,118; and 7,671,350 as well as WO 00/37928 all incorporated herein by this reference. See also U.S. Published Application No. US-2008-0152079.
The shields for these devices, typically attached to the nose of the instrument, serve to protect the user of the device from radiation. Radiation limits are usually established by regulations which may vary by jurisdiction.
For handheld XRF devices with lower power x-ray tubes (e.g., below about 4 watts and producing about 40 keV), reaching a radiation limit is not as big a concern as with higher power x-ray tubes (e.g., those producing 50 keV and above) used in some industries. This is because at tube voltages of 50 keV and higher, a greater amount of x-ray radiation between 40 keV and 50 keV is produced. These energies are harder to shield while still maintaining the small size and minimal weight needed for a handheld device. Thus there are more x-rays emitted from the device, than in lower voltage portable XRF devices. In addition, the 40 keV-50 keV x-rays are more likely to scatter multiple times within a sample, rather than be absorbed by the sample, and then be directed back towards the operator. Also, in some instruments, the power output by the x-ray tube can be varied (e.g., between 40 keV and 50 keV).